Nemanja Radonjic came on as a second half substitute to score in the 89th minute and earn Marseille a 2-1 win in a breathless Ligue 1 encounter with Brest on Friday.
Coach Andre Villas-Boas has now guided the former European champions to their fourth successive league win.
It lifted the second-placed side onto 28 points, five behind Paris Saint-Germain who face Monaco on Sunday.
"I think it was our best game, but also the most stressful," admitted Villas-Boas.
"Amazing. We played well, this is the first time I have nothing to complain about."